President Trump spoke at the Pentagon Memorial on Monday to commemorate the sixteenth anniversary of the 9/11 terror attacks.
"America cannot be intimidated, and those who try will soon join the long list of enemies who dared to test our mettle," Trump said to a crowd including family members of victims.
"Where they left a mark with fire and rubble Americans defiantly raise the stars and stripes."
"Our whole world changed. America was under attack," the president said of the Tuesday in 2001. "It was the worst attack on our country since Pearl Harbor."
"This was an attack on civilians, innocent men, women, and children," he reminded, pledging we will never forget the victims.
Trump took a hard line with enemies of America, including terrorists.
"American forces are relentlessly pursuing and destroying the enemies of all civilized people," he assured.
The president and first lady also stood for a moment of silence outside the White House Monday morning at the moment the first plane flew into the north Twin Tower in New York City.
Secretary of Defense Jim Mattis also gave a tribute to the terror victims.
"We never asked for this fight, but we are steadfastly committed to seeing it through," Mattis said in his remarks.